Re: [Qemu-devel] [RFC] sync NIC's MAC maintained in NICConf as soon as emualted NIC's MAC changed in guest

[Jason Wang]

On 09/22/2013 04:35 PM, Zhanghaoyu (A) wrote:
> Hi, all
>
> Do live migration if emulated NIC's MAC has been changed, RARP with wrong MAC 
> address will broadcast via qemu_announce_self in destination,
> so, long time network disconnection probably happen.
>
> I want to do below works to resolve this problem,
> 1. change NICConf's MAC as soon as emulated NIC's MAC changed in guest
> 2. sync NIC's (more precisely, queue) MAC to corresponding NICConf in NIC's 
> migration load handler
>
> Any better ideas?

As Michael points out. The only possible solution is to use do it inside
the guest instead of qemu ( and using a pv device). You can have a look
at my RFCs in
http://lists.nongnu.org/archive/html/qemu-devel/2013-03/msg01127.html
which let virtio driver send the gARP. Xen, Hyperv does the same thing.

The point is qemu does not know how the macs was used. So your method
only solves the issue partially becuase:

- A card can have several macs, see virtio_net and e1000's mac table and
it can be overflowed also.
- Vlan could be used so we need to send tagged gARP instead of untagged.
>
> Thanks,
> Zhang Haoyu
>